Dynamic models of several mechanical systems are used for the analysis of specific robotic mechanisms. Two different situations may be encountered. The first situation is when the robot’s command system, based on Lagrange’s differential equations, calculates the corrections of command parameters of the actuators at short intervals of time. This model includes both the characteristics of the mechanical structure and those of the actuators and transmission. A second situation is encountered during the motion planning, when a model is needed to calculate both engine parameters and inertial forces which are applied to the mechanical system during the operation. Consequently, in this study, a d’Alembert-Newton model is used for extended dynamic analysis of a new constructive solution of a parallel mechanism. The dynamic model of a HEXA parallel mechanism has been developed using the abovementioned theory, and further, the dynamic inverse solution has been obtained. The numerical results were obtained using an original algorithm. This dynamic model allows the estimation of power absorbed by each actuator and also the loading control for each kinematic chain of the HEXA parallel mechanism. Knowing the variation of driving torque, for all the six actuators of the mechanism, allows the user to choose an optimal trajectory, such as avoiding excessive loading of a single kinematic chain.
Abstract.Workspace geometric modelling of a new type of 6RSS parallel manipulator is described below. In the beginning, the researches undertaken in this area by other authors are highlighted and then a definition of this type of mechanisms is provided. The structural model of the 6RSS manipulator is briefly described. Inverse geometric model and translation subspace methods are used in order to determine the dimensions that define the workspace volume of the parallel manipulator. The reachable workspace is defined as a subset of the whole workspace in relation with the positions achieved by the characteristic point.
Management of intraductal papillary and mucinous pancreatic neoplasms. Mucinous and papillary pancreatic cystic neoplasm is a controversial pathology both from a diagnostic point of view and from a management point of view. These recommendations will include diagnostic modalities and criteria (endoscopic, imaging and histopathological), conservative management of cystic pancreatic, mucinous and papillary neoplasm and its absolute and relative surgical indications. High risk factors (high risk stigmata) for which surgery is indicated without further exploration are positive cytology for malignancy, jaundice, dilation of the main pancreatic duct over 10 mm in diameter and the presence of the wall nodule over 5 mm. For patients with a diameter of the main pancreatic duct between 5 and 9.9 mm or a cyst larger than 4 cm, surgery has a relative indication, and for asymptomatic patients with a cyst smaller than 4 cm without parietal nodules, a Conservative management is more appropriate.Our goal is to develop a protocol based on the new European recommendations published by the European Study Group on Cystic Pancreatic Tumors, in order to facilitate the early diagnosis and treatment of patients. We also want to sensitize the specialists and make them aware of the need to develop centers dedicated to hepato-biliary-pancreatic pathology and to improve the logistical means.
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